# The Naked Scientists Forum

### Author Topic: molarity help  (Read 3465 times)

#### pandapower

• First timers
• Posts: 1
##### molarity help
« on: 25/09/2006 04:07:17 »
hi people

If a solution has a Ca(OCl)2 concentration of 5g per 100 ml of solution, what is the molarity of hypochlorite?

can some one explain how to do so? thanks

#### rosy

• Neilep Level Member
• Posts: 1018
• Chemistry
##### Re: molarity help
« Reply #1 on: 25/09/2006 09:32:59 »
Calculate the formula weight of the calcium hypochlorite.
To get the number of moles of calcium hypochlorite, divide the 5g by the formula weight.
The molar concentration (mol per dm3) will be 10 x the number of mol in 100ml.

The concentration of hypochlorite is twice that of the calcium hypochlorite since there are two equivalents of hypochlorite in the formula.

Does that help?

#### dtx

• First timers
• Posts: 3
##### Re: molarity help
« Reply #2 on: 02/10/2006 14:54:07 »
Set up your problem using conversion factors like this:  (5g Ca(ClO)2/100mL) x (1 mol/molar mass Ca(ClO)2) x (1000mL/1L) = molarity of your solution.

Once you cancel all of the units, you will be left with mol/1L, which of course is the molarity.  The 100mL in the denominator of the first term and the 1000mL in the numerator of the last term give you the "10x" Rosy was talking about.  Just so you understand why, molarity is always based on a liter.  To make a 1M solution of something, you add 1 mole of solute to a volumetric flask, then fill to the 1L mark with water.

#### lightarrow

• Neilep Level Member
• Posts: 4586
• Thanked: 7 times
##### Re: molarity help
« Reply #3 on: 11/10/2006 11:42:24 »
quote:
Originally posted by pandapower

If a solution has a Ca(OCl)2 concentration of 5g per 100 ml of solution, what is the molarity of hypochlorite?
It's so difficult to open any kind of simple chemistry book? I think you take less time than waiting an answer from us!

#### The Naked Scientists Forum

##### Re: molarity help
« Reply #3 on: 11/10/2006 11:42:24 »